Walt's Corner

Standard waiver of responsibility applies: This is how I did it. I have over 38 years of experience in electronics. Your safety is your responsibility. Always seek professional guidance if you have any questions. Never guess when it comes to your life.

This is part 2 of a 2-part series. Part 1 can be viewed here. It also contains the complete parts listing with links in case you are interested. If you want to jump to the final video of the install completed, you can see it right here.

To recap my purpose, I am not installing this to be able to charge my trailer as I am traveling. I don’t have an issue with that. Between the existing truck power and solar panels, I usually get at least a 7 amp charge that basically keeps the battery topped off. If battery is not topped off, the solar panels will ensure it is. This charger is designed to be used while driving, so it includes an extra 12 volt input that gets applied when the vehicle key is in the run position. Turn your vehicle off and that 12 volts goes away, turning off the charger. That will keep it from depleting your towing vehicle’s battery to charge the house battery. But that is not how I designed my install.

My purpose of this charger is to provide a high amperage charge to the house battery in the event that I happen to go 3-4 days without good sunshine and I want to be able to have enough power to get me through the night. I can run the truck for 20 minutes and that will be enough. This will eliminate the need to carry around my small generator as a back up that I never use. This provides me peace of mind while not carrying the backup inverter.

This being the case, I have a switch installed inside the trailer that is used to apply that 12 volts to the charger. Plug only the this power plug into the truck, not the regular trailer pigtail, start the truck, and flip that switch inside and the charger will be energized and charging.

Instructions from Renogy, and just really good advice in general, you want your DC to DC charger to be as close to the battery as possible. This is why I chose to install it in the same cubby as the rest of my power components. I am making all my own cables, so before I can cut my wire to no more/no less than needed, I needed to know where the charger would be physically mounted.

First step was to remove all the power. I removed the solar panels and battery from the system. No more power and the physical removal of the battery provides a decent amount of space to work in.

I chose to place it next to my DC to AC Inverter, which required lowering my inverter a little. It was about dead vertical dead center on the cubby wall. I removed and lowered it to where it would provide the charger with the 5 cm of surrounding space required for proper heat dissipation. Now that my location was known, I went ahead and found the route my cable would take from the tongue to the separate components involved. I used the existing trailer pigtail as a guide since the connector on the truck is very near the connector where that pigtail is plugged into. The frame of the tongue is hollow and provides access holes. Perfect.

Back to the power center, I removed the existing battery cables for the terminal and tied some wire to them. I pulled them out from the front/exterior and as I did it pulled that wire through that I tied to them. This will provided me an easy way to fish the new and existing wires back through. Now that I have all the cables running from the battery compartment to the tongue, I was able to cut the wires to the length I needed in order to manufacture a properly sized pigtail.

Before working on the truck-side of this project last weekend, I started off with 50 feet each of red and black wire. After install I only had about 3 feet of red and 2 feet of black left. I used more of the red because of fuse placement. I installed a 100 amp fuse on the truck side and 80 amp fuse on the trailer.

I was sure to place all shrink tubing and connector assemblies on the cables prior to using a torch to solder the stripped ends into their respective plug ends. Terminal lug on the battery side and SBC120 pins on the pigtail side. Now that the cables are complete I started at the point where the cables get fished through from the outside to the inside of the trailer. Kind of the middle point from a construction view point. On the outside I then installed some plastic cable protections around both cables and ran the pigtail end of the cables through the access points of the tongue frame and had it exit just under the propane tank holding area. Mirroring the existing trailer cable.

Finally, I slid the SBC120 pins into their connector and slide the connector in the housing of the connector holder and secured. I used cable ties to keep the red and black wires together. This newly constructed cable connects directly to the charger as the DC input.

Having done this, it was a simple job of connecting the components into the existing system via my bus bars I manufactured when I installed the LiFe BT battery.

I left some lights and the radio on all night so that I’d have less than full battery the next day for proper testing. Battery (200AH) was down to 88% (174AH). Turning the charger on provided a 56 amp charge to the battery. It charged back up to 97% in 20 minutes. At that point the charger reduced the amperage to 30AH, then 20, as it reached full charge. I’m a Happy Camper.